1. Field of the Invention
The present invention relates to motor graders, and, more particularly, to control systems and the operation of motor graders to overcome draft.
2. Description of the Related Art
Motor graders, also known as “road graders”, are used in many aspects of road construction and maintenance, as well as for material moving and finish grading for general purposes. Motor graders can be used to shape the ground for general purposes, such as developing ditches, and for shaping the final surface of a roadbed. In maintenance operations, motor graders can be used, for example, to clean and reform ditches, to reshape and contour worn road beds, to spread added material on a roadbed, to remove snow and the like. To achieve such versatility in operation, motor graders are highly controllable with respect to the set up and operation thereof.
A motor grader can include an articulating frame having a rear frame portion carrying a motor, transmission, operator cab and the like, and an elongated front frame portion that includes adjustable front wheels and an earth scraping blade which commonly is referred to as a moldboard. Carrying and adjustment structure for the moldboard allows adjustments for angle, tilt and roll of the moldboard as well as lateral side shifting.
Manual controls or input devices are provided for various operating and adjustment aspects, such as steering, speed, moldboard positioning, frame articulation, wheel angle orientation and power input.
To achieve a desired earth shaping result, the operator of a motor grader has many adjustments available, including moldboard elevation and extension, moldboard angle relative to the frame axis, moldboard tilt relative to a vertical axis and/or moldboard roll or lean relative to a horizontal axis.
As can be appreciated, adjustment of one aspect of a motor grader operation can impact performance in other aspects. For example, when a motor grader is cutting material with the moldboard at an angle relative to the longitudinal axis of the machine, material is moved along the length of the moldboard and deposited to one side. In such an operation, the forward or leading edge of the moldboard is referred to as the “toe” and the trailing edge is referred to as the “heel”. Depending on conditions of the earth or other material being moved, the topography, the angle of the moldboard and the like, the motor grader may be pulled away from an intended straight path toward the side of the moldboard toe, even if steering is adjusted for straight ahead operation. Absent compensatory adjustment in machine operation, the machine may deviate from the desired path of operation, which is referred to as draft. Side shifting the moldboard also creates draft. The more off center that the moldboard is, the greater the draft forces are.
A skilled operator has a variety of options available to adjust the motor grader operation to compensate for draft. For example, the operator can adjust the steering and/or change the drive system performance to apply greater pulling power in front of the toe of the moldboard, thereby overcoming draft. The operator also can adjust lean of the drive wheels in front of the moldboard. It is desirable to make the adjustments before the material pass begins; however, an inexperienced operator may not recognize before the pass is begun what adjustments are required nor the severity of the adjustments required to overcome draft. As a pass is made with the motor grader, even greater skill is required to detect changing conditions affecting draft, select an appropriate corrective measure or measures and enact the corrective measure or measures while continuing to observe machine operation and assess other changing operating conditions. Skilled operation of a motor grader involves initial setup, constant observation and assessment, and readjustment as necessary to achieve the desired result in the least amount of time.
Even a skilled motor grader operator can have difficulties in rapidly changing conditions. A less skilled operator can have difficulty achieving the desired result even in less challenging conditions due to the complex interactions of possible adjustments. Identifying the proper adjustment or adjustments and performing the adjustment or adjustments in a timely fashion can be difficult even for skilled motor grader operators.
What is needed in the art is a system for rapidly identifying and carrying out needed adjustments to compensate for motor grader draft during operation even in rapidly changing conditions.